Astronomers explain why disk galaxies eventually look alikeSeptember 17, 2013
Iowa State's Curtis Struck and IBM's Bruce Elmegreen are studying how galaxies evolve from the clumpy example on the left to the smooth example on the right.
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“Geologist [I'm Climate Change]”
Since: Mar 07
#1 Sep 18, 2013
A look over orbit data of stars in the Hipparcos dataset provides interesting proof in passing in our own ringed barred spiral.
Older stars have a high ellipticity as a result of the bar & dual spiral arms from the bar.
Mid age stars are mostly a disc with elliptical orbits (see sun). The younger stars are mostly near circular (hyades etc.) which the mid age stars such as the sun either pass through via overtaking or get overtaken depending on where they are in the orbit.
The original ~11 billion year barred spiral became a ringed barred spiral before the sun's age and was an almost perfect theta shape prior to the interaction with the Magellanic clouds.
Our galaxy now has prominent spiral arms only due to the tidal interaction with the magellanic clouds.
Have a nice day: Ag
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